1.the numbers are good.
2. The IS is good
3. Some 35/40.8, 35/41 and most 35.5/40.8 show this contrast characteristic. Nothing to worry about. The arrows appear and disappears depending on the viewing distance or light obstruction.
My biggest concern is that the stone is too clean. Just make sure there is no cloud or twinning wisp that causes haziness. I like this better than the other one.
You may wish to check if the 'feather' (fracture plane - of some kind) at 6 o'clock, on the right side of the tip of the respective arrow, breacks the surface on the uderside of the girdle. If it does, perhaps I would still consider this promissing diamond - with advice ...